1. Field of the Invention
The present invention relates generally to overcoatings for magnetic data storage disks and magnetic head/slider constructions. More particularly, the present invention relates to wear resistant and lubricating overcoatings for magnetic data storage disks and magnetic head/slider constructions.
2. Description of the Related Art
The recent and continuing advances in computer and information technology have been made possible not only by the correlating advances in the functionality, reliability and speed of semiconductor integrated circuits, but also by the correlating advances in the storage density and reliability of direct access storage devices (DASDs) employed in digitally encoded magnetic data storage and retrieval.
In that regard, the storage density of direct access storage devices (DASDs) employed in digitally encoded magnetic data storage and retrieval is typically determined, at least in part, by a separation distance of a magnetic head/slider construction from a rotating magnetic data storage disk into which rotating magnetic data storage disk digitally encoded magnetic data is written and from which rotating magnetic data storage disk digitally encoded magnetic data is read. Similarly, the reliability of direct access storage devices (DASDs) employed in digitally encoded magnetic data storage and retrieval is also in part determined by the ability to maintain a close, uniform and asperity free separation distance of the magnetic head/slider construction from the rotating magnetic data storage disk. In addition, however, the reliability of direct access storage devices (DASDs) employed in digitally encoded magnetic data storage and retrieval is also in part determined by the wear and tribologic characteristics of: (1) a static magnetic head/slider construction resting upon a static magnetic data storage disk; (2) an accelerating magnetic head/slider construction taking off from an accelerating magnetic data storage disk; and (3) a decelerating magnetic head/slider construction landing upon a decelerating magnetic data storage disk, since the foregoing static, accelerating and decelerating conditions are at least occasionally encountered within all installations of direct access storage devices (DASDs) and are routinely encountered within direct access storage device (DASD) installations which are operated transiently.
Towards the goal of improving reliability of direct access storage devices (DASDs) through providing optimal wear and tribologic characteristics of magnetic head/slider constructions with respect to magnetic data storage disks within those direct access storage devices (DASDs), it is known in the art of direct access storage device (DASD) fabrication to overcoat the air bearing surface(s) of at least either a magnetic head/slider construction or a magnetic data storage disk with a coating which either imparts improved wear characteristics to the magnetic head/slider construction and/or the magnetic data storage disk or imparts improved tribologic properties to the magnetic head/slider construction with respect to the magnetic data storage disk.
Several disclosures may be found in the pertinent arts pertaining to improvement of either the wear characteristics or the tribologic properties of magnetic head/slider constructions or magnetic data storage disks through overcoating those magnetic head/slider constructions or magnetic data storage disks with various overcoating compositions.
For example, Grill et al., in U.S. Pat. No. 5,159,508 disclose a magnetic head/slider construction having a wear resistant protective coating formed thereon, the wear resistant protective coating being formed from a thin adhesion layer formed upon the magnetic head/slider construction and a thin amorphous hydrogenated carbon layer formed upon the thin adhesion layer. The wear resistant protective coating may be employed both when fabricating the magnetic head/slider construction and when employing the magnetic head/slider construction within a direct access storage device (DASD) magnetic data storage enclosure.
In addition, Lee et al., in "The Effect of Chemical and Surface Properties of Hydrogenated Carbon Overcoats on the Tribological Performance of Rigid Magnetic Disks," IEEE Trans. on Magnetics, Vol. 29 (1), January 1993, pp. 276-81, disclose the effects of hydrogen content in the range of about 16 atomic percent to about 53 atomic percent within hydrogenated carbon overcoatings on tribologic properties of magnetic data storage disks overcoated with those hydrogenated carbon overcoatings. At the higher levels of hydrogen content disclosed, there was observed improved tribologic properties of the magnetic data storage disks as determined by magnetic head slider drag testing.
Further, Bogy et al., in "Enhancement of Head-Disk Interface Durability by Use of Diamond Like Carbon on Overcoats on the Slider's Rails," Digests of the Magnetic Recording Conference, September 1993, D5, disclose that diamond like carbon coatings when coated onto slider rails of sliders provide sliders with wear durability increase factors of from 50 to 200. The wear durability increases were obtained, however, with a concomitant increase in friction of the sliders with respect to thin film magnetic data storage disks.
Yet further, Wang et al., in "Tribological and Recording Performance of Carbon-Coated Thin Film Head Sliders on Unlubricated and Lubricated Thin Film Media," IEEE Trans. on Magnetic, Vol. 30 (6), November 1994, pp. 4125-27, disclose and compare the use of facing target sputtering (FTS) methods and DC magnetron sputtering methods for forming diamond like carbon coatings on thin film magnetic head/slider constructions. While diamond like carbon coatings formed through facing target sputtering (FTS) methods provide diamond like carbon coatings which are generally tribologically superior to diamond like carbon coatings formed through DC magnetron sputtering methods, thin film head/slider constructions having formed thereupon diamond like carbon coatings formed through either facing target sputtering (FTS) methods or DC magnetron sputtering methods provide tribologically superior thin film magnetic head/slider constructions in comparison with thin film magnetic head/slider constructions having no diamond like carbon coating formed thereupon.
Still yet further, Wang et al., in: (1) "The Effect of Hydrogen in Carbon Overcoats on the Tribology of the Head-Disk Interface," IEEE Trans. on Magnetics, Vol. 31 (6), November 1995, pp. 2919-21; and (2) "The Interaction of Lubricant With Hydrogenated Carbon," Digests of Intermag '96 Conference, July 1996, HA-07 disclose results of experiments employing contact stop/start (CSS) testing of hydrogenated carbon coated magnetic data storage disks overcoated with perfluoropolyether lubricant compositions, as a function of hydrogen content within the hydrogenated carbon coatings. It was observed that higher levels of hydrogen within the hydrogenated carbon coatings provided improved perfluoropolyether lubricant composition mobility over the magnetic data storage disks.
Yet still further, Chen et al., in U.S. Pat. No. 5,567,512 disclose a thin film magnetic data storage disk having formed thereupon a nitrogenated carbon coating, as well as a method for fabricating the nitrogenated carbon coating upon the thin film magnetic data storage disk. The nitrogenated carbon coating so formed imparts superior wear resistance to the magnetic data storage disk.
Finally, Jahnes et al., in U.S. Pat. No. 5,569,506 disclose: (1) a magnetic data storage disk having a textured surface which provides a magnetic data storage disk exhibiting a low level of static friction with respect to a magnetic head/slider construction positioned upon the magnetic data storage disk; and (2) a method for fabricating the magnetic data storage disk having the textured surface. Within the method for forming the magnetic data storage disk, there is employed a discontinuous textured interlayer formed between a pair of conformal amorphous carbon layers formed over the magnetic data storage disk.
As may be determined through analysis of the foregoing references, it is common within magnetic head/slider construction fabrication and magnetic data storage disk fabrication to employ overcoatings which impart to magnetic head/slider constructions or magnetic data storage disks either wear resistance characteristics or lubricating properties, but typically not simultaneously both wear resistance characteristics and lubricating properties.
It is thus in general towards the goal of forming form use within direct access storage devices (DASDs) magnetic head/slider constructions and magnetic data storage disks which have formed thereupon overcoatings which simultaneously provide to those magnetic head/slider constructions and magnetic data storage disks both improved wear resistance characteristics and improved lubricating properties that the present invention is generally directed. More particularly, the present invention is also directed more specifically towards the goal of forming with minimal process complexity for use within direct access storage devices (DASDs) magnetic head/slider constructions and magnetic data storage disks which have formed thereupon overcoatings which simultaneously provide both improved wear resistance characteristics and improved lubricating properties to those magnetic head/slider constructions and magnetic data storage disks.